We agreed to save the brain for last: "If anything looks even remotely like a cause of death, we're not opening that head." On the table, a partially mummified corpse. Its fingers were yellow and shrivelled; there were black tattoos on grey skin. "It's brain soup in there. I'd rather not know."

There was a ladle nearby in case we wanted to find out later.

The autopsy is an examination of the body as machine, a hardware hack on hopeless equipment. As with some bugs you may never find out what went wrong. There may be several ailments: a pancreatic cancer, say; a cirrhotic liver. The evidence of death is incontrovertible, but the cause is an eel slipping out of your hands.

And the pathologists are one step up from a butcher. I have seen evisceration performed where the cutting scalpel was held in a man's curled fist, not gingerly balanced between fingertips as a surgeon would do. This is not the fine art of dissection.

But what dissection could do the brain justice, or any of the organs? We sneak around biological functions with our words, our diagrams of neural networks, our schemata of the digestive system. Because the body speaks chemistry, an assembly language we cannot understand - and our top-level object-oriented speech will never agreeably classify - they are held captive by a picture we have created in words. The only way to understand the viscera is to be elbow-deep in them.

So this is how it works, the hack, the evisceration: cut around the neck and down the torso, peel back the layers of skin and fat. Open the ribcage - no special equipment needed here, just an ordinary breadknife. Peel back the skin of the neck, dissect out the tongue and throat. The organs are freed and lifted out, all the way back to the spine. The liver is bigger than you thought it was; the lungs smaller.

The father of morbid anatomy, Giovanni Morgagni, is widely quoted in pathology circles, "Those who have dissected many bodies have at least learned to doubt; when others, who are ignorant of anatomy and do not take the trouble to attend to it are in no doubt at all." The first thing I doubted when in the morgue was whether the origin of life could ever have been created, because even with all our intelligence taking them apart is so easy, and putting them back together so impossible. The second thing I doubted was that life could ever not have been created: how could this happen in absentia of some creative power, some unseen magic, a sentient but impalpable force instead of infinite iterations of physical laws?

Several months ago I met a musician who theorised that all who work with the dead are either atheists or drunks. Perhaps that's the mask we want people to see: hard, imperturbable, made of strong character and stronger stomachs. Every glass of single malt straight up in a cold glass numbing the sound of rib shears and skull saws. Lone wolves and cynics wrapped up in their own implosion.

This is one of the ghosts hanging over the living in the morgue. The others include the popular press, popular opinion, religion. The Sun is there, screaming about us, we happy few, we ghoulish mutilators. The Mirror, too, because we are organ thieves, taking everything but the soul. The faith of the Native Americans, who note how we are now soiled and will never wash clean.

It's true; once earning this knowledge you cannot undo it. Having your hands in someone like this is real intimacy. Being in love can happen every day. Raising children is as common as muck. But the tenders of the dead have touched something few people will. If love is like Bellow's description of "neediness, the awareness of incompleteness, the longing for wholeness," death is love to the nth power. Hardware obsessives sneer at software programmers and end users who interact with their beautiful machines through only the keyboard and mouse; similarly, the pathologists and their like are set well apart.

Like hackers, the hours are odd and obsessive. It's hard to get into a serious romantic relationship and harder still to maintain it, unless your partner is in a related field or insane. The work swallows you, tact is right out the window, and you find yourself discussing decapitation over lunch, laughing. Someone points out that your blood oranges-and-balsamic vinegar salad looks like a tub of organs. You laugh some more. It is well known that your colleagues will die young; that's the way it is. You do not think about who will have to do their autopsies.

Some people keep the eviscerated organs in a single lump for examination; others do it in blocks. They're pulled out and put in a washing-up basin. The ladle is for the fluids that collect in the midsection, which are poured down a drain and chased by hose water. Some knot the intestine to keep its contents in; others tie it off with string. By this time you're breathing through your nose because the smell doesn't bother you anymore. It smells of bad breath during a hangover. It smells of chitlins before they're washed, fried and eaten by hungry children.

Someone combs the deceased's hair forward, peels back the skin, cuts open the skull. They take out the brain and bring it to you. Attending to the shell end are the mortuary assistants, whose job is as much about the survivors as it is about the hack. They stuff the skull with cotton wool because the organs, when the pathologist is done, go into a black bin liner in the torso. They slot the skull back on and sew up the skin. It's a lovely stitch they do, with those giant curved needles; like the embroidery technique of faggotting that brings two pieces of fabric together, the flaps of skin are welt-stitched. The thread is pulled up tight to keep fluids in. They comb the hair over and decide whether the next of kin could stand to see this empty thing lumpen on a table.

But that is not the hack. Over to the side, there are sinks, scales and cutting boards. Organs are weighed and cut through, examined and washed. A chunk out of the liver for histology. There's the spleen, who knows what it does, it has a distinctive odor. Confirmation of past intrusions by doctors of the living: yes, there's where her gall bladder would have been. There's that old heart attack from the medical history. Admiration for those who fiddled with the machine but left it mostly intact, and some derision for them as well. They never get to see it like this past the first years of med school. They must be jealous - they never get to explore.

The superficiality of life is embodied in the real surfaces of the membranes. There are many people who go through life only looking at what is displayed on the monitor, happy with that, happy to have access to such an agreeable, if mysterious, appliance. There are others who want to open it up and know everything, and they are drawn to this work. The pathologists are born, not made.

Examining the organs takes as long as you want. There are some who blaze through in fifteen minutes. There are those who handle each part gingerly, as if it were friable.

Everyone has a signature way of doing it: the first postmortem I saw, the pathologist had the organs in a single block and examined them back-to-front, from kidneys forward. For some time I thought this was the only was it was done.

Ask yourself: is the cartilage of the neck damaged? Is there food or liquid in the lungs? The heart is sliced through, the valves and vessels examined for tears and blockage. There is more, a litany of questions for each way a human could possibly die. But the best hackers cannot describe what they do. It is a routine as much a part of how the hands work as writing a word or tipping a spoon up to sip its contents. It is there, and real, but inexplicable. The pathologist has achieved complete absorption into the machine.

The pieces are then distributed to the histologists, the toxicologists, those specialists who will examine this or that connection in detail until they have come up with an answer that, while not always true, is true enough.

Morgagni reminds us of the certainties of life (that we will die) and the uncertainties of death. When the whores who have been murdered and left in the Peak District to rot are brought to us, maggots pour out of the eyes, mouth, foramen magnum, vagina. Some escape and crawl under the lip of the dissection tables; we've got enormous purple bug zappers for when the pupae open.

The post-Enlightenment clinical gaze sought to tease out the tangible spaces of the body where its "secrets, invisible lesions and the very mystery of origins lie hidden." We examine their bodies with care, because there is no more difference between the dead than there is in different computers. Cray supercomputer or Commodore PET, it's just the same components arranged differently. We do our best to answer questions because someone has to, someone has always had to, from the women in Edwardian London who dressed the dead for two and six, to the witchy spinsters in the Appalachians who knew what herbs, which cloths, were needful to their task. And we kind of like the whores, because there is so much to learn about them, and because the cause of death is often more clear-cut than with the others.